1. Field of the Invention
The present invention relates generally to an anti-skid brake control system for an automotive vehicle for controlling braking pressure to be built-up in a wheel cylinder of an automotive brake unit. More specifically, the invention relates to an actuator unit for delivering controlled pressure to an associated wheel cylinder in order to provide optimal braking performance of the vehicle.
2. Description of the Background Art
In the typical construction of an actuator unit employed in a circuit of an automotive anti-skid brake system, an inlet valve (EV valve) and an outlet valve (AV valve), a pressure accumulator, a fluid pump, a fluid reservoir, one-way check valves and so forth are provided for adjusting fluid pressure to be delivered to the wheel cylinder according to wheel slippage in order to maintain wheel slippage in an optimal range, i.e. 10% to 20%.
As will be appreciated, a substantially high pressure, e.g. 300 atm is active in the hydraulic brake circuit during application of a brake. For substantially high pressure, the components forming the actuator unit for the anti-skid brake control system are required to have a satisfactorily high leak-proof construction. For this reason, respective components, such as an EV valve, AV valve and so forth as well as fluid path piping are formed independently of each other. Such independently formed components are assembled into one unit by means of a connecting or housing block. In such prior proposed actuator units, since each of the independently formed components has to be provided with sufficient strength under high fluid pressure and to have sufficient leak-tight construction, each of the components is necessarily bulky. Therefore, the assembled unit is substantially bulky to cause inconvenience in mounting in a substantially limited space on the vehicle. Furthermore, such bulky unit is necessarily heavy in weight for causing weight problem.